Overclocked Electromancer (110) [Modern Horizons 3 Commander]

At the beginning of combat on your turn, you may pay {E}{E}{E}. If you do, put a +1/+1 counter on this creature. Whenever this creature attacks, double its power until end of turn. Whenever this creature deals combat damage to a creature, if that creature was dealt excess damage this turn, you get X {E}, where X is that excess damage.